A mobile apparatus can be controlled to perform an operation as a function of a position of the mobile apparatus. An example of such an operation is ejecting a liquid onto a medium for printing an image or fabricating a device. The accuracy to which the position of the mobile printing apparatus must be known depends at least in part upon what is being printed and the quality of the resulting output that is required. For example, the print quality of a sign that is to be viewed at a long distance does not require as high a degree of positional accuracy of printing as does a poster-sized print of a photographic image. In addition, the placement of different portions of an image that are separated by white space is not as critical as the placement of different portions of an image that are adjacent to each other and printed on separate printing swaths. With regard to functional printing for fabricating a device, the alignment of adjacent swaths for the printing the device in multiple passes can affect the performance of the resulting device.
Commonly assigned, co-pending U.S. patent application Ser. No. 13/686,986 filed Nov. 28, 2012, entitled “Mobile Apparatus with Local Position Referencing Elements” by Greg Burke; co-pending U.S. patent application Ser. No. 13/686,992 filed Nov. 28, 2012, entitled “Method of Positioning a Mobile Apparatus” by Greg Burke; co-pendingU.S. patent application Ser. No. 13/686,998 filed Nov. 28, 2012, entitled “Mobile Apparatus with Local Position Referencing Structure” by Greg Burke; and co-pending U.S. patent application Ser. No. (13/687,008 filed Nov. 28, 2012, entitled “Determining a Position of a Mobile Apparatus” by Greg Burke and Gary Kneezel, the disclosures of which are herein incorporated by reference, disclose local positioning references for a mobile apparatus. Some of such local positioning references can have an accuracy of a few thousandths of an inch. Such accuracy is sufficient for placement of different portions of an image that are separated by white space. However, for printing of adjacent swaths of an image at high image quality, an accuracy of approximately one thousandth of an inch can be required.
Therefore, a need exists for a more accurate way of determining the position of a mobile printing apparatus for printing an image or other item in multiple passes, such that adjacent printed swaths are aligned without a readily perceptible effect due to misalignment. A need also exists for a mobile printing system that provides maintenance and preferably also replenishment for the mobile printing apparatus.